SPRINGFIELD, Mass. — Merriam-Webster, the oldest dictionary publisher in America, has turned itself into a social media powerhouse over the past few years. Its editors star in online videos on hot-button topics like the serial comma, gender pronouns and the dreaded “irregardless.” Its Twitter feed has become a viral sensation, offering witty — and sometimes pointedly political — commentary on the news of the day.

Kory Stamper, a lexicographer here, is very much part of the vanguard of word-nerd celebrities. Her witty “Ask the Editor” video contributions, like a classic on the plural of octopus, and personal blog, Harmless Drudgery, have inspired a Kory Stamper Fan Club on Facebook. One online admirer has carefully tracked minute changes in her hair (which, for one thing, is purple).

But the company remains very much a bricks-and-mortar operation, still based in this small New England city where the Merriam brothers bought the rights to Noah Webster’s dictionary in the 1840s and carried on his idea of a distinctly American language. And this month, Ms. Stamper, the author of the new book “Word by Word: The Secret Life of Dictionaries,” was more than happy to offer a tour of some of the distinctly analog oddities in the basement.

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A first edition of Noah Webster’s A Compendious Dictionary of the English Language (1806).CreditTony Luong for The New York Times

She walked me through a hallway that seemed to double as a museum of superannuated filing cabinet technology. She offered a glimpse of the dungeonlike storage room used as a podcast studio and cheerfully pointed out some of the creepier company heirlooms, like mangy historical dioramas donated by local schoolchildren and an inflatable dictionary with arms and legs, created for a long-ago promotional campaign.

But the real jaw-dropper was the Backward Index, which includes some 315,000 cards listing words spelled … backward.

“It was conceived of as another way of shuffling information,” Ms. Stamper said of the index, which seems to have been produced intermittently from the 1930s to the ’70s. “Basically, someone sat here and typed up all the entries backwards. And then went crazy.”

Craziness is a bit of a leitmotif in “Word by Word.” The book, published last week by Pantheon, mixes memoiristic meditations on the lexicographic life along with a detailed description of the brain-twisting work of writing dictionaries. The Atlantic called it “an erudite and loving and occasionally profane history of the English language” that’s also “a cheerful and thoughtful rebuke of the cult of the grammar scolds.”

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The second edition of the Webster’s New International Dictionary, which a 1934 poster advertised as “one of the thickest books ever printed.”CreditTony Luong for The New York Times

Ms. Stamper calls it “a love letter to dictionaries in English,” if one that allows for some mixed feelings.

“People have so many fears about what their use of language says about them,” she said. “When you talk to people about dictionaries, they often start talking about other things, like which words they love, and which words they hate. And it’s perfectly fine to hate parts of the language.”

Ms. Stamper, 42, grew up in Colorado and majored in medieval studies at Smith College. When she interviewed at Merriam-Webster in 1998, she was puzzled to learn the job involved writing definitions.

“I just thought, ‘Why would you need to do that?’” she recalled. “Hasn’t the dictionary already been written?”

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Inside a file at Merriam-Webster, an editorial note from the 1950s on the word “cracker” declared that it “could not be defined as a ‘biscuit’ nor as a ‘wafer.’”CreditTony Luong for The New York Times

“Word by Word” describes her own initiation into the art of lexicography, which involves wrestling with the continuous evolution of language. She walks the reader, chapter by chapter, through different aspects of a definition, including grammar, pronunciation, etymology and more.

Her first definition, by her recollection, was “blue plate.” Since then, she estimates, she has had a hand in hundreds of thousands of others.

“Take,” which she wrestled with for a month, was the longest in column inches. (It’s also one, she notes wryly, that very few people will ever read.)

“God,” which she revised for the company’s unabridged dictionary (now being updated online only), took the longest — four months — and involved not just extensive reading but consultation with clergy members, theologians and academics, who often responded to her email queries with long philosophical disquisitions.

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Empty file cabinets in the basement at Merriam-Webster’s headquarters.CreditTony Luong for The New York Times

Which leads to an important point. Dictionaries are often seen as argument-settling arbiters of truth. But their job, Ms. Stamper notes, isn’t to say what something is, but to objectively and comprehensively catalog the many different ways words are used by real people.

Ms. Stamper has no patience for self-styled purists who quail at “irregardless” — an actual word, she notes. (She is O.K. with ending sentences with prepositions as well as — brace yourself — split infinitives.) But she also describes being caught up in some higher-stakes fights.

One chapter takes an uncomfortable look at the racial assumptions baked into a Merriam-Webster definition of the color term “nude.” Another recounts the furor that erupted in 2009 when it added a subdefinition to its entry on “marriage,” noting uses to refer to same-sex unions that weren’t necessarily legally sanctioned.

That brought reams of hate mail, but most interactions with readers are friendlier. When Merriam-Webster began its videos, the heavy-breathing fan mail prompted her to create an “Ask the Editor Video Hotness Chart.”

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Webster’s Seventh New Collegiate Dictionary, from 1969, was asymmetrically bound so it could hold itself up — an innovation that failed to catch on because of design flaws.CreditTony Luong for The New York Times

“People would write in saying, ‘The editor with the glasses is so hot,’” she said. “Which is hysterical, since we all wear glasses.”

Stalkers who show up at the offices in Springfield, alas, may have trouble finding actual people. Ms. Stamper telecommutes from her home outside Philadelphia. During the visit, the halls were eerily deserted. No heads popped above cubicles. Only a few faintly murmuring voices were heard.

But at the center of the main upstairs work area stands a howling mass of irreplaceable historical chatter: the Consolidated Files.

The files, kept in red cabinets that snake around the middle of the room, contain millions of citations: small slips of paper documenting individual word uses, drawn from newspapers, books, radio, packaging and other sources, stretching from the 1980s back well into the 19th century.

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In addition to the updated digitized databases at Merriam-Webster, there is an analog vestige known as the Consolidated Files, containing millions of citations of word uses.CreditTony Luong for The New York Times

These days, lexicographers work from an updated digitized database. But Ms. Stamper opened a drawer and pulled out a favorite “pink,” as editorial notes are called, from the 1950s sternly declaring that the word “cracker” “could not be defined as a ‘biscuit’ nor as a ‘wafer.’”

“This just sums up the job so well,” she said in a sub-sotto-voce whisper.

If dictionaries are a form of information technology, the building is in some ways a catalog of obsolescence. A downstairs gallery includes a 1934 poster advertising the second edition of the Webster’s New International Dictionary, billed as “one of the thickest books ever printed.” (The technology needed to bind it, Ms. Stamper said, no longer exists.)

There are also oddities like an asymmetrically bound Seventh New Collegiate from 1969, designed so it could hold itself up — an innovation that failed to catch on, probably because if you open it too far from the center, it falls over.

The dictionary industry itself has been listing of late, as printed dictionaries have given way to online dictionaries, many of them free. Merriam-Webster, a subsidiary of Encyclopaedia Britannica, itself announced layoffs just as she was finishing her manuscript. (It currently has 70 employees.)

There are only about 50 lexicographers working at dictionary companies in the United States today, Ms. Stamper estimated. But their work, she believes, remains as vital as it was in Noah Webster’s day.

“There’s something to having a bunch of nerds sitting in an office dispassionately reading lots and lots of material and distilling the meaning of a word as it’s been used in lots of places,” she said. “It really is this weird democratic process.”

Correction:

An article on Thursday about Merriam-Webster, the oldest dictionary publisher in America, described the current edition of the company’s unabridged dictionary incorrectly. It remains in print; it is not an online-only publication. (Future updates to the dictionary, however, will be made only online.)